There are numerous methods and appliances for the qualitative and quantitative testing of textile fibres. In many test methods, the unordered fibre material, for example cotton in flock form, cannot be measured immediately, but must first be processed into nonwoven webs having a parallelized fibre position. These webs are then used as test samples for obtaining measured quality values on the fibre material and, in the form of continuous nonwoven webs, as a preliminary step in the manufacture of threads or yarns from the fibre material.
Known appliances for the opening of fibre flocks consist conventionally of a pair of feed rollers and of an opening drum. A subsequent cylinder receives the opened material, and then stores it or transports it further. The pair of feed rollers ensures controlled material guidance which is imperative in view of the high degree of opening necessary in the fibre flocks. In such opening appliances for fibre flocks, there is a need to produce the desired sliver, if possible, without the fibre being damaged. Appliances of this type according to the state of the art, for example cards, have a high throughput, but, at the same time, the fibres are nevertheless damaged to a considerable extent. In cards according to the state of the art, it is also already known to structure the feed rollers, for example by the formation of spirals on the surface of the feed rollers or on a clothing having elements arranged in the direction of run and resembling small hooks. These structures have primarily the function of preventing the fibres from adhering to the rollers. A selective retention of the fibres is not possible with these structures, thus leading to increased fibre damage in the fibre samples obtained thereby.
During the feed Of unordered fibre material by means of a pair of feed rollers to an opening roller provided with a "card clothing", the fibre material is opened and a uniform nonwoven is obtained from it. During this, the pair of feed rollers moves preferably at a lower circumferential speed than the opening roller. At least one feed roller can likewise be provided with a "card clothing", the elements of this "clothing" extending counter to the direction of rotation of the feed roller. The pair of feed rollers retains the still unordered fibre material selectively along a line, while the "card clothing" of the opening roller continuously seizes some of the fibres and opens them. A nonwoven is then obtained from these on the subsequent folding roller.
In textile technology, the "card clothing" of a roller is meant to describe phrase the attachment of a series of narrow bands on the outer surface of the roller, which are equipped with small teeth or small hooks usually inclined either in the direction of rotation or counter to this. Likewise, a corresponding design of the outer surface of the roller itself, which can be obtained, for example, by engraving or rolling and by means of which small teeth or small hooks are attached to the outer surface of the roller, can also be designated as a clothing. For the sake of brevity, such small teeth and small hooks will be combined hereafter under the term "small hooks".
In the method mentioned, the individual fibres of the unordered fibre material are retained only along a line. Now if the opening roller draws on a longer fibre, then the remaining fibres behind the retaining line are drawn towards the feed rollers. There is consequently always an excess of fibre material between the feed rollers, thereby increasingly reducing the selective effect of the clothing on one of the two feed rollers. Finally, the fibre material is clamped again. Now if a fibre is seized by the opening roller, then the retaining force is so high that the fibre is torn off. The resulting nonwoven web therefore no longer fully possesses the quality features of the unordered fibre material and consequently can no longer be considered as a completely representative test sample. However, the torn-off pieces of the long fibres also have a quality-reducing effect on the yarn when the nonwoven web is used as a preliminary stage in yarn production.
Furthermore, EP-B1-0,247,420 discloses an appliance for ordering the ends of fibres for fibre-length measurement, in which a nonwoven is introduced into a needle-type transport device consisting of a plurality of needle combs and is transported intermittently by this to a gripper device, by means of which a sample can be extracted from the nonwoven. The needle-type transport device in this known appliance consists of a "needle bed". This term is meant to describe a series of parallel combs which are equipped with needles and which can be moved transversely relative to the comb direction. While the nonwoven is at rest, the comb of the needle bed which is the foremost in the transport destination direction is moved into the last position of a lower comb series having an opposite direction of transport. The comb located in the foremost position and belonging to this lower comb series is simultaneously moved back into the needle bed as the rearmost comb. During transport, the needle bed has no appreciable influence on the orientation of the fibres in the nonwoven. The needle bed serves merely to retain the nonwoven while a part sample is being obtained in order to determine the fibre-length distribution.
Further needle-type transport systems, already on the market, of N. Schlumberger & Cie. NSC are known, for example under the designation "Intersectingstrecke GN 6" ["Intersecting drafting frame GN 6"] (Company prospectus Intersectingstrecke GN6, pages 8/9, and Company prospectus GN6, page 5) or "Kettenstrecke GC13"["Chain drafing frame GC13"] (Company prospectus, page 5), in which, instead of a gripper (as in EP-B1-0,247,420), a pair of rollers is mounted, and by means of this slivers or nonwovens can be combed, unfelted and folded. However, these known needle-type transport systems or needle-type drafting frames are not suitable for the opening of unordered fibre material.
The object on which the invention is based is to provide a method by which a uniform nonwoven web can be produced from unordered and unopened fibre material better than in the disclosed methods, along with the greatest possible preservation of the fibre quality, especially the fibre-length distribution.
Further advantageous embodiments of the invention are described below.